57: Pediatric Anesthesia

CHAPTER 57 Pediatric Anesthesia



Rita Agarwal, MD, Sola Olamikan, MD



1 What are the differences between the adult and pediatric airways?


See Table 57-1.


TABLE 57-1 Differences Between the Adult and Pediatric Airways
























Infant Airway Significance
Obligate nose breathers, narrow nares Infants can breathe only through their noses, which can become easily obstructed by secretions.
Large tongue May obstruct airway and make laryngoscopy and intubation difficult.
Large occiput Sniffing position achieved with roll under shoulder.
Glottis located at C3 in premature babies, C3-C4 in newborns, and C5 in adults Larynx appears more anterior; cricoid pressure frequently helps with laryngeal visualization.
Larynx and trachea are funnel shaped Narrowest part of the trachea is at the vocal cords; the patient should have an ETT leak of <30 cm H2O to prevent excessive pressure on the tracheal mucosa, barotrauma.
Vocal cords slant anteriorly Insertion of ETT may be more difficult.

ETT, Endotracheal tube.



2 Are there any differences in the adult and pediatric pulmonary systems?


See Table 57-2.


TABLE 57-2 Differences in the Pediatric and Adult Pulmonary Systems



























Pediatric Pulmonary System Significance
Decreased, smaller alveoli Thirteenfold growth in number of alveoli between birth and 6 years; threefold growth in size of alveoli between 6 years and adulthood
Decreased compliance Increased likelihood of airway collapse
Increased airway resistance, vulnerability to smaller airways Increased work of breathing and disease affecting small airways
Horizontal ribs, pliable ribs and cartilage Inefficient chest wall mechanics
Less type 1, high-oxidative muscle Babies tire more easily
Decreased total lung capacity, faster respiratory and metabolic rate Quicker desaturation
Higher closing volumes Increased dead-space ventilation


3 How does the cardiovascular system differ in a child?



image Newborns are unable to increase cardiac output (CO) by increasing contractility; they can increase CO only by increasing heart rate.

image Babies have an immature baroreceptor reflex and limited ability to compensate for hypotension by increasing heart rate. Therefore they are more susceptible to the cardiac depressant effects of volatile anesthetics.

image Babies and infants have increased vagal tone and are prone to bradycardia. The three major causes of bradycardia are hypoxia (most common cause), vagal stimulation (laryngoscopy), and volatile anesthetics. Bradycardia decreases CO.


4 What are normal vital signs in children?


See Table 57-3.



TABLE 57-3 Normal Vital Signs in Children

image


5 When should a child be premedicated? Which drugs are commonly used?


Children may have fear and anxiety when they are separated from their parents and during anesthetic induction. Children who are 2 to 6 years old who have had previous surgery or no preoperative tour and education or who fail to interact positively with health care providers in the preoperative area should be premedicated. Children who are anxious during induction may suffer from negative postoperative behavioral changes. Children who receive premedication with midazolam have fewer negative postoperative changes than children who do not.



6 Should parents be allowed to accompany their children to the operating room?


Young children may become anxious and frightened when they are separated from their parents. Allowing parents to accompany children to the operating room (OR) may facilitate anesthetic induction in some cases. Parents and children should be educated and prepared for what to expect, and parents should be prepared to leave when the anesthesiologist believes it to be appropriate. Anxious, reluctant, or hysterical parents are a hindrance. An anesthesiologist who is not comfortable with parental presence probably should not allow them to be present. An uncooperative, frightened child may not benefit from parental presence. Although allowing parents to be present during induction of anesthesia is beneficial to the parents, premedication with midazolam actually is associated with lower levels of anxiety in the child. The benefit of both premedication and parent presence during anesthesia appears to be additive.



7 What medications are available for premedication?


See Table 57-4.



TABLE 57-4 Routes of Administration for Premedications in Children

image


8 Describe the commonly used induction techniques in children



image Inhalational induction is the most common induction technique in children younger than 10 years who do not have intravenous (IV) access. The child is asked to breathe 70% nitrous oxide (N2O) and 30% oxygen for approximately 1 minute; sevoflurane is then turned on. The sevoflurane concentration can be increased slowly or rapidly.

image Rapid inhalational induction is used in an uncooperative child. The child is held down, and a mask containing 70% N2O, 30% oxygen, and 8% sevoflurane is placed on the child’s face. This unpleasant technique should be avoided if possible. Once anesthesia has been induced, the concentration of sevoflurane should be decreased.

image Steal induction may be used if the child is already sleeping. Inhalational induction is accomplished by holding the mask near the child’s face while gradually increasing the concentration of sevoflurane. The goal is to induce anesthesia without awakening the child.

image IV induction is used in a child who already has an IV line in place and in children >10 years. Typical medications used in children are thiopental, 5 to 7 mg/kg; propofol, 2 to 3 mg/kg; and ketamine, 2 to 5 mg/kg. EMLA cream (eutectic mixture of local anesthesia) applied at least 90 minutes before starting the IV infusion makes this an atraumatic procedure.


9 How does the presence of a left-to-right shunt affect inhalational induction and intravenous induction?


A left-to-right intracardiac shunt leads to volume overload of the right heart and pulmonary circulation, resulting in congestive heart failure and decreased lung compliance. Uptake and distribution of inhaled agents are minimally affected; onset time for IV agents is slightly prolonged.



10 How about a right-to-left shunt?


Right-to-left shunting causes hypoxemia and left ventricular overload. Patients compensate by increasing blood volume and hematocrit. It is important to maintain a high systemic vascular resistance (SVR) to prevent increased shunting from right to left. Such shunts may slightly delay inhalation induction and shorten the onset time of IV induction agents.



11 What other special precautions need to be taken in a child with heart disease?



image The anatomy of the lesion(s) and direction of blood flow should be determined. Pulmonary vascular resistance (PVR) needs to be maintained. If the PVR increases, right-to-left shunting may increase and worsen oxygenation, whereas a patient with a left-to-right shunt may develop a reversal in the direction of blood flow (Eisenmenger’s syndrome). If a patient has a left-to-right shunt, decreasing the PVR may increase blood flow to the lungs and lead to pulmonary edema. Decreasing the PVR in patients with a right-to-left shunt may improve hemodynamics. Conditions that can increase shunting are listed in Table 57-5.

image Air bubbles should be meticulously avoided. If there is a communication between the right and left sides of the heart (ventricular septal defect, atrial septal defect), air injected intravenously may travel across the communication and enter the arterial system. This may lead to central nervous system symptoms if the air obstructs the blood supply to the brain or spinal cord (paradoxical air embolus).

image Prophylactic antibiotics should be given to prevent infective endocarditis. Recommendations for medications and doses can be found in the American Heart Association guidelines.

image Avoid bradycardia.

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May 31, 2016 | Posted by in ANESTHESIA | Comments Off on 57: Pediatric Anesthesia

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